Many electronic retail (and institutional, e.g. libraries) anti-theft security systems in commercial use utilise activatable ferromagnetic memory labels. Such labels are removed or deactivated at purchase time so that such labels will not trigger an alarm system attached to a magnetic field interrogation zone typically at the exit doorway of the establishment. For example, Peterson U.S. Pat. No. 4,158,434--Electronic Status Determining System For Goods, discloses such a system. A major problem inherent in such systems is that a suitable specialized label must be applied to every retail article for which security protection is desired. In a retail environment such as a supermarket, for example, the profit margins are too low to economically justify such application of specialized labels.
Weighing systems have been proposed in the past as security means for retail self-serve checkout systems. For example, Clyne U.S. Pat. No. 4,373,133--Method For Producing A Bill, Apparatus For Collecting Items, And a Self-Serve Shop, Mergenthaler U.S. Pat. No. 4,779,706--Self-Service System, and Johnson U.S. Pat. No. 4,787,467--Automated Self-Service Checkout System, disclose weighing system as security means for retail self-serve checkout systems. However, all these latter inventions suffer from the limitation that should a customer steal a product by hiding said product within one's clothing or carried bags, the latter inventions would not detect the theft.
Poisson U.S. Pat. No. 4,405,856--Apparatus For Recording Identifying Data Concerning The Use Of A Credit Card, Cheque Or The Like, discloses the weighing of a customer for security reasons in financial transactions, but does not develop the idea with respect to retail security concerns.